Answer:
1-5: Make it 1 unit tall
6-10: Make it 4 units tall
11-15: Make it 1 unit tall
16-20: Make it 0 units tall (Change nothing)
21-25: Make it 5 units tall
Explanation:
1-5: 1 (1 number)
6-10: 7, 9, 9, 10 (4 numbers)
11-15: 13 (1 number)
16-20: (0 numbers)
21-25: 21, 23, 23, 25, 25 (5 numbers)